The present invention relates to a geared motor having a hypocycloid-type speed reducer and a case made of a resin material.
For example, a geared motor that is an electric motor with a speed reducer is used as a driving source for a seat lifter for an automobile.
Japanese Patent Application Unexamined Publication No. 2007-533282 A based on PCT Application No. PCT/EP2005/003716 discloses an actuator including a worm provided on an output shaft of a drive motor, a spur wheel meshing with the worm, and an eccentric bearing pin formed integrally with the spur wheel and having an axis offset from an axis of the spur wheel. The eccentric bearing pin is engaged in a bearing opening of a wobble plate. The wobble plate has a swivel arm clearance-fitted into a radial groove of an intermediate plate. When the spur wheel is rotated through the worm, the wobble plate and a gear formed integrally with the wobble plate are turned around an axis of the spur wheel without being rotated about the axis. The gear of the wobble plate is turned around the axis of the spur wheel while meshing with an internal teeth of a driven wheel. Therefore, when the gear is turned around the axis of the spur wheel one time, the intermeshing portion of the gear and the internal teeth is moved to make one-time turn so that the driven wheel is caused to rotate by a difference between the number of teeth of the gear and the number of teeth of the internal teeth. As a result, the rotation number of the driven wheel is reduced relative to the rotation number of the spur gear.
U.S. Patent Application Publication No. 2007/0161451 A1 discloses a geared motor including a worm provided on an output shaft of an electric motor, a worm gear meshing with the worm, an eccentric hollow shaft rotatably connected with the worm gear, and an eccentric gear mounted on the eccentric hollow shaft so as to be capable of turning around the eccentric element while meshing with an internal teeth of an output element. When the worm gear is rotated to cause the eccentric gear to turn around the eccentric hollow shaft, the intermeshing portion of the eccentric gear and the internal teeth of the output element is moved to make one-time turn so that the output element is caused to rotate by a difference between the number of teeth of the internal teeth of the output element and the number of teeth of the eccentric gear. As a result, the rotation number of the output element is reduced relative to the rotation number of the worm gear. The eccentric gear is prevented from rotating by a coupling element.